1 Technical Field
The present invention relates to reactors that employ a laminated core as a magnetic core.
2 Description of Related Art
As a magnetic core of a reactor, a laminated core may be employed which is formed by laminating a plurality of soft-magnetic ribbons made of a magnetic sheet steel, an amorphous alloy or a nanocrystalline alloy. Employing the laminated core, it is easy to increase the saturation magnetic flux density of the magnetic core. However, at the same time, the permeability of the magnetic core is prone to become high. Therefore, in the case of employing the laminated core, gaps are generally formed in the laminated core across the magnetic path of the laminated core.
However, with the gaps formed in the laminated core, fringing flux is generated outside the gaps in the lamination direction. Consequently, eddy current is generated on side surfaces of the laminated core in the vicinities of the gaps, i.e., generated in the soft-magnetic ribbons located at ends of the laminated core in the lamination direction, thereby increasing the eddy current loss. Moreover, due to generation of the fringing flux, it becomes easy for magnetic flux to concentrate on the soft-magnetic ribbons located at the ends of the laminated core, thereby increasing the hysteresis loss.
To solve the above problem, Japanese Patent Application Publication No. JP2007012647A discloses a complex magnetic core that is comprised of a laminated core and a plurality of dust cores. Each of the dust cores is formed by compacting ferromagnetic powder whose surface is insulation-treated. Moreover, gaps are formed between the dust cores. Consequently, with the dust cores that have a high electrical resistance, it is possible to suppress the generation of eddy current, thereby reducing the iron loss.
However, in the complex magnetic core disclosed in the above patent document, the dust cores have a relatively low permeability. Consequently, the magnetic reluctance of the entire complex magnetic core is increased, thereby increasing the loss of the complex magnetic core.